**2. Diets**

Several diets have been available for patients with diabetes. Some of them are tested in randomized clinical trials while others have been put forth by nutritionists or other professionals. The main focus of these diets is weight loss as obesity is also a growing global pandemic and is a major risk factor for several severe medical conditions including T2DM. Large randomized controlled studies such as Look Action for Health in Diabetes (Look AHEAD) study, Finnish Diabetes Prevention study and Diabetes Prevention Program Research group had focused on reducing body weight and incidence of diabetes.

## **2.1 Look AHEAD study**

This study included 5145 patients and continued for eleven years (2001–2012) in the US [2]. The major goals for this study were to reduce body weight by 7% and increasing physical activity to ≥175 mins/week. Participants of this study were ethnically diverse (African Americans, Hispanic and Native American/Alaskan native) and were diabetic. Co morbidities included hypertension and cardiovascular disease (CVD) [2]. There were three phases of the study with nutritional interventions, lifestyle and behavioral modifications. The nutritional interventions were as follows: Phase I (1–12 months) patients were encouraged to replace two of their meals with shakes, one snack with a bar and consume low energy dense foods. The energy goals were dependent on the body weight of the individuals: <250 lbs. were limited to 1200-1500Kcal and those ≥250 lbs. were limited to 1500-1800 kcal/day [2]. Medications were given to patients who failed to show weight reduction in the first 6 months. Physical activity goals were set at moderately intense activity for 175 minutes/week. Either self monitoring or in person monitoring was conducted at regular intervals. Weight regain was addressed by further counseling and replanning the diet. In Phase 2 (2 years −4 years) and Phase 3 (5 years and above) patients were monitored and were expected to maintain the goal of 10% body weight loss following the diet and activity [2]. Patients successfully lost weight and were physically fit with this diet lifestyle change, however, they could not maintain the weight loss [3]. Patients also improved some of the conditions for diabetic patients [3].

#### **2.2 Finnish diabetes prevention study**

This study was started in 1998 to determine if an intensive exercise-diet program can prevent or delay the onset of T2DM [4]. A total of 522 patients were in the study and divided into the control and intervention groups. The diet modification included reduction of total fat consumption to <30% with less than 10% saturated fats and high fiber intake [4]. The physical activity goal was 4 hours/week of walking, bicycling or other exercise [5]. The focus of this study was to follow patients to see if there was decrease in the development of diabetes and reported that there was 43% decrease in the risk of development of diabetes. After thirteen years, this study reported that the recommended interventions successfully prevented the progression of T2DM on a long term basis [6].

#### **2.3 Diabetic prevention program research group**

This study was conducted across 27 clinics in the US. There were 1079 ethnically diverse patients [7]. The goal was to reduce body weight by 7% in the first 6 months by increasing physical activity and consuming a diet with less fats and saturated fats. They reported a 58% reduction in the incidence rate of diabetes [7].

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*Nutritional Interventions: Diet Modifications, Nutritional Supplements, Complementary…*

Other long term randomized clinical trials like Da Qing IGT and Diabetes Study have also shown that diet and exercise interventions are very efficient in reducing

The recommended intake of carbohydrate is 45% - 65% per day. Choices with

Glycemic Index (GI) rises with increase in glucose levels [10]. Factors affecting GI are rate of digestion, cooking method, type of carbohydrate, fat content, protein content and acidity of the food. High starchy foods digest faster so there is high and quick release of glucose. Lower GI foods does not rise the blood glucose levels as quickly. Insulin response and glucagon inhibitors are also affected. High fiber delays the digestion process, increases CCK, incretins and satiety. Lower glycemic diet does not reduce body weight but reduces HbA1c and improves insulin sensitivity [15, 16]. This diet can only have moderate effects in controlling postprandial hyperglycemia. It did not have any effect on the body weight but decreased HbA1C by 0.5% [10].

Fat consumption is targeted by this diet as diets high in fats can reduce insulin sensitivity and increase endogenous production of glucose by the liver and production of proinflammatory cytokines [10, 17]. This diet focuses more on consumption of ≤30% calories from fat which would be around 50 g of fat for 1500Kcal/day diet. The type of fat consumed determines the damage caused more than the quantity of fat especially with respect to glycemic control [18]. It induced weight loss and had very little effect on glycemic control [10]. However, the long term effects of weight

Decreasing calories is another method to reduce body weight, thereby, decreasing the risk of developing T2DM. The recommendation for those seeking this diet option consumed 400 to 800 calories/d of high quality protein and carbohydrates fortified with vitamins, minerals and trace elements. Decreased body weight and

HbA1C were reported with high rate of body weight regain [10].

decreased refined carbohydrates, no added sugar, increased intake of grains, legumes, vegetables and fruits were recommended along with limiting high fructose syrup and sucrose. The sources of carbohydrates are not a major factor in the glycemic response as randomized trials showed no difference in glycemic response when sources of carbohydrates was substituted [9]. However, it is important to note that complex sources of carbohydrates are beneficial in determining the circulating glucose levels after meals. Post prandial glucose levels are reflective of the amount of sugar not the type of sugar [10, 11]. Fructose is metabolized in the liver and can affect lipid metabolism so limiting fructose consumption is recommended. Low carbohydrate diet is very effective in decreasing body weight [12, 13]. Patients on this diet not only lost body weight but also decreased HbA1C, however, they were prone to gain weight very quickly. Low carbohydrate diet maybe a short term solution to manage T2DM and can comprise of fiber, vitamins and minerals. Patients on such diet have to be checked for their lipid profile, renal function and protein intake

*DOI: http://dx.doi.org/10.5772/intechopen.94645*

the risk of developing diabetes [8].

**2.4 Low carbohydrate diet**

regularly [14].

**2.6 Low fat diet**

**2.7 Very low calorie diet**

loss may reduce or delay the onset of T2DM.

**2.5 Low glycemic index diet**

*Nutritional Interventions: Diet Modifications, Nutritional Supplements, Complementary… DOI: http://dx.doi.org/10.5772/intechopen.94645*

Other long term randomized clinical trials like Da Qing IGT and Diabetes Study have also shown that diet and exercise interventions are very efficient in reducing the risk of developing diabetes [8].
